def townhall
can_upgrade_to flying_townhall keep

def flying_townhall
class soldier
cost 12 16
food_provided 1
hp_max 400;  1200/3
time_cost 135
can_upgrade_to townhall
food_cost 0
airground_type air
speed 1.5
damage 0
is_repairable 1
is_healable 0
transport_volume 99
corpse 0
